Pyrometric cone



Sept 3, 1938. -H. E. co VAN ET AL 9, 2

PYROMETRIC coma Filed July 30, 1936 GeazyeAzBoZe HarzyETb nt Patented Sept. 13, 1938 UNITED STATES PATENT OFFICE PYROMETRIC CONE Ohio Application July 30, 1936 Serial No. 93,456

2 Claims.

This invention relates to improvements. in pyrometric cones, a primary object being to provide cones characterized by their uniform straightness,

dimensional accuracy, freedom from Warpage and 5 responsiveness, in the matter of deformation to narrow predetermined temperature limits.

Pyrometric cones are used in the ceramic arts primarily for the purpose of providing convenient and economical means for determining the ma- 1=0 turity' of ceramic articles when fired. Such cones comprise flat-surfaced bodies in the general form of trihedral pyramids and possess such a composition, form and mass so that the same will weaken or soften under elevated temperature conditions.

temperature is sufficiently high and the time factor long enoughto cause deformation of such a cone, the operator of the kiln, by observing the physical condition of the cone, may ascertain w quite accurately the maturity of the ware undergoing heat treatment. Pyrometric cones while not a substitute for thermocouples, nevertheless, constitute heat measuring devices which are quite Widely used as practical guides in obtaining correct firing of ceramic bodies.

Such cones, when made in accordance with present methods of manufacture, are not characterized with that degree of uniformity by which complete reliance can be placed by a kiln operator 3Q on their thermal deformation points. This is in the main attributable to the presently used method for producing the same, which is known in the art as the plastic method, and comprises mixing certain ceramic raw materials including,

2 among others, plastic clay, feldspar, flintand Whiting with an organic binder and water until a condition approximating maximum plasticity is secured. These materials, while in a plastic state, are then shaped by means of molds into H cone formation. While still ina formative or plastic state, these initially formed cones are removed from the molds by hand operation and are placed on pans or trays for delivery to a drying or baking zone, in which the cones are heated to: a temperature and for a sufiicient period of time to remove moisture therefrom and to cause their hardening into a desired state of permanency.

These operations quite commonly result in the 50 production of cones lacking uniformity in shape and dimensions. This may be due to several causes among which are: Irregularities in the pockets of the molds in which the plastic cones are formed, due to wear or other causes; the

55 removal of the plastic cones from the mold pock- In kiln operation, when the internal ets, eifected manually, for the purpose of placing the molded plastic cones on drying trays, and wherein the operator in lifting or handling the cones may cause the latter to stretch, foreshorten or bend beyond their intended and originally o molded shapes, with the result that cones of a given class Will not respond uniformly to the same thermal conditions of kiln operation, and by reason of the fact that plastic clay has a high shrinkage factor when dried through heating, and this 10. also presents a condition which results in variation in cone dimensions.

It is therefore an object of the present invention to produce pyrometric. cones with the use of substantially dry materials through forces of 55, compression or compaction, whereby accurately shaped and dimensioned cones may be commercially manufactured and which will be uniformly responsive to predetermined thermal conditions.

Another object of the invention resides in the Q provision of a pyrometric cone wherein the major longitudinal axis thereof, when the cone occupies its normal operative position within a kiln, is disposed at an angle of approximately 82 with respect to the horizontal or base end of the cone, whereby when the cone is positioned in a receive i-ng pad, its body will be automatically offset fromthe vertical to secure the correct angle of inclination or tilt normally required in the setting of cones of this kind, so that when the cone body is heated to a predetermined temperature, it will bend, flex or deform offering a physical indication of the temperatures surrounding the same.

A further object of the invention resides in the 5 provision of apyrometric cone produced as a result of a press operation in which movable die heads having angularly related surfaces are operated to compress or compact the substantially dry powdered materials from which the cones are 49 formed, the operation being such as to eifect the formation of cones of uniform hardness or density throughout the length thereof, particularly in the regions of reduced cross section, so that such cones may be shipped or handled without undue breakage and, moreover, when in use will accurately respond to given thermal conditions.

For a. further understanding of the invention, reference is to be had to the following description and the accompanying drawing, wherein:

Fig. 1 is a perspective view of a pyrometric cone formed in accordance with the present invention;

Fig. 2. is a side elevation thereof, disclosing the same mounted in a receiving pad or base; 5

Fig. 3 is a similar view disclosing the cone when bent or distorted through the action of elevated temperatures;

Fig. 4 is a bottom plan view of the cone;

Fig, 5 is a top plan view;

Fig. 6 is a perspective view of the punch and die members employed in the formation of the cone;

Fig. 7 is a vertical longitudinal sectional View taken through the die and punch mechanism;

Fig. 8 is a vertical transverse sectional view taken through said punch and die members and disclosing the same in their final positions of cone compression.

Referring more particularly to the drawing, the numeral l designates the pyrometric cone of the present invention. The same comprises a body in the general form of a trihedral pyramid, having planar, substantially triangular outer surfaces, said body being of such composition, form and mass so that the same will weaken or soften under elevated temperature conditions, causing flexing or bending of the body, as indicated in Fig. 3, to offer physical indications of given temperature conditions.

The cone body, instead of being produced by plastic molding operations, as heretofore, is formed by a press operation with the use of substantially dry materials. The composition used in the manufacture of the cones comprising the present invention may vary somewhat but, in general, the cones are formed from a mixture comprising the following ingredients, namely, pre-shrunk (calcined) clay, feldspar, flint, whit ing, silica, iron oxide and a glass, to which is added an organic binder such as dextrine or glucose. In practice, the binder may be combined with water to an extent not substantially in excess of 5% by weight of the totalingredients present, whereby to assist the action of the binder in uniting the basic materials when the same are subjected to compaction in a power actuated press. This relatively small amount of water does not sensibly affect the apparent dryness of the powdered materials when the latter are not under compression, nor is it present in sufficient amounts .as to render such materials plastic in the ordinary sense of the term. It will be understood, therefore, that the term dry pressing does not preclude the employment of a sufficient amount of water in connection with the body forming materials to assist in the compaction of such materials when subjected to press operations.

A press suitable for carrying out the present invention forms the subject matter of our copending application Serial No. 93,457 and has been illustrated in Figs. 6 and '7, wherein the upper punch member is designated at 2, a stationary die at 3, and a lower punch member at 4. The die is stationarily supported in connection with the frame of an ordinary tablet producing press, and is formed with a slot 5 which extends completely through the die from the top to the bottom thereof, the said slot, when viewed in plan, has the form of a right angle triangle.

The punch members are provided with heads 5 which are relatively movable with respect to each other and the operations are timed so that the heads may enter the slot 5 and approach each other relatively to compact the cone-forming materials, introduced into the slot 5 therebetween. The upper end of the head of the lower punch member terminates in a flat inclined surface bounded by base, altitudinal and hypotenusal edges 8, 9 and I0 respectively, the general plane of the surface I being inclined at an angle of substantially 30 with respect to the horizontal. Likewise, the lower end of the head of the upper punch member is formed with a complemental cone pressing surface II, which has the same shape and configuration as the surface I of the lower head, but is reversely inclined to a uniform degree above the horizontal with respect thereto, so that the altitudinal edge l2 of the surface II will register with the hypotenusal edge In of the lower head forming a triangular shaped recess I3 between said heads when the latter are advanced, as shown in Fig. 8, to their extreme positions of compression.

Due to the formation of the inclined surfaces 1 and H of the punch heads, the dry materials, comprising the body composition of the cone, will readily distribute themselves with uniform density throughout the length of the recess or opening l3 during the application of press pressures to said materials, thus producing pressed cones of uniform hardness and density throughout the length thereof. Also, due to the formation of the punches and the associated die, the cones formed thereby are characterized by their exceptional straighteness and dimensional accuracy as well as their uniform density. It is to this fact that the cones formed in accordance with the present invention respond so accurately .and uniformly to given thermal conditions, there being no perceptible difference in the behavior of any cone of a given size under corresponding elevated temperatures. The surface ll of the upper punch head is provided with a removable plug, indicated at M, having an embossed outer surface, which during the formation of a cone in the press, produces on one side thereof a size identifying symbol as indicated at [5, and also a transverse line or depth mark l6. By noting the symbol, and given size of cone may be readily determined, and by having the symbol impressed in the side of the cone, rather than in the front surface thereof, the size number and the cone may be readily identified even after the cone has deformed, as shown in Fig. 3, under the action of kiln temperatures.

Since cones of this type are usually placed in clay pads or pats, as indicated at H in Fig. 2, when used in a kiln, it is necessary in order to obtain uniform response that the lower or base ends of the cones should be inserted into the plastic material constituting the pad or pat to a uniform or definite extent. Hitherto, this has been done largely by mere guess on the part of the kiln operator with resultant variables in operation. In accordance with the present invention, however, the operator is provided with a positive guide as to the depth of insertion of the cones into the plastic pads or pats so that the desired uniformity of operation may be attained.

Since the'altitudinal edges 9 and [2 of the punch pressing surfaces are not truly horizontal, as shown particularly in Fig. '7, but are inclined at a slight angle with respect to the horizontal, the cone formed thereby, as shown in Fig. 2, has its major longitudinal axis it, when the cone occupies an upright position, located at an angle of 82 with respect to the plane of the base I!) of the cone, which, theoretically considered, occupies a horizontal plane when the cone is normally positioned. Operating standards require that a cone must be tilted with respect to the vertical so that its major axis will be located at an-angle of 82 with respect to the horizontal.

With cones of prior manufacture, the obtaining of this angle has been largely a matter of experience, skill and care used by the operator in setting the cones in a pad or pat. However, by the method and apparatus of forming the cone of the present invention, the correct angle of tilt is automatically attained and inherently formed into the cone so that when the latter is forced into a plastic pad or pat and properly embedded therein as indicated by the depth mark I 6, the operator will be assured of the correct angularity of the major axis of the cone without further effort or pains.

In summary, therefore, the present invention provides a cone which through its mode of formation will be better adapted for the ascertainment of kiln temperatures than has been heretofore obtained with cones of conventional manufacture. Through the provision of the punch members, it will be observed that the cone first of all possesses the true form of a trihedral. pyramid having surfaces of strict dimensional accuracy, of uniform straightness, freedom from warpage and of uniform density and hardness throughout the full length thereof. Ordinary molded cones, produced by the plastic method, are very apt to be bent or warped due to the handling of the cones when in a plastic or formative state, when removing the same from mold pockets or otherwise handling the same. Again, plastic molded cones frequently vary in length and do not possess the uniform density or hardness throughout their length as is obtained by the present invention. Also, our improved cones when removed from the press inherently contain their major axes at the correct angle of inclination which the cone should occupy when placed in the kiln. Other advantages reside in the provision of the identifying symbol on one of the side surfaces of the cone and so located that it may be observed even after the cone has been thermally bent or deformed, and in the provision of the depth mark for correctly ascertaining the degree to which the cone should be embedded in the plastic supporting pad or mat by which the cones are carried in group formation when used in a kiln firing operation.

In addition to the advantages above set forth, the cones may be very economically manufactured and usually do not require any heat treatment upon removal from the press, in order to harden or to render their form permanent, although such additional heat treatment may be used on the cones if desired.

What is claimed is:

1. A pyrometric cone substantially in the form of a three sided pyramid having flat triangular front, side and base surfaces, and indicating means provided on one of the side surfaces, the major axis of the cone being disposed at such an angle to the plane of the base as to cause the entire cone body to incline toward the front whereby said cone when it is softened by heat will bend in the direction of its inclination and said indicating means including adepth indication extending substantially parallel to the base.

2. A pyrometric dry pressed cone substantially in the form of a three sided pyramid having flat triangular front, side and base surfaces, the major axis of the cone being disposed at such an angle to the plane of the base as to cause the entire cone body to inc-line toward the front whereby said cone when it is softened by heat will bend in the direction of its inclination.

HARRY E. CO VAN. GEORGE A. BOLE. 

